Brood X (10) of the 17-year Periodical Cicadas (Magicicada spp.; family Cicadidae) have come and gone in Ohio leaving behind oviposition damage (flagging) as a reminder of their spring fling. Annual Dog-Day Cicadas (Neotibicen canicularis; family Cicadidae) are now arriving on the scene along with their nemesis, Cicada Killer Wasps (Sphecius speciosus).
During this week’s Tuesday morning BYGL Zoom Inservice, Curtis Young (OSU Extension, Van Wirt County) reported that he heard his first dog-day cicada singing in northwest Ohio over the 4th of July Weekend. I heard my first cicada in the southwest part of the state this past Monday.
Colette Gabriel (Ohio Department of Agriculture (ODA) Division of Plant Health) reported during an online meeting on Wednesday that the ODA Asian Giant Hornet Online Reporting Portal is already receiving pictures of cicada killer wasps from concerned Ohioans thinking the killers are murderers; the Asian giant hornet (Vespa mandarinia). The Asian giant hornet has not been found in Ohio or anywhere else in North America outside of the extreme northwest corner of Washington State and in Canada near Vancouver. However, the hornet did not fly from Asia to those locations.
It’s important to remain vigilant. Our ODA was proactive in 2020 with setting up an online reporting website; the only state outside of Washington to do so. You can learn more about it by reading the BYGL Alert titled “Asian Giant Hornet (a.k.a. "Murder Hornet"): It’s Not in Ohio, but Remain Vigilant” posted on June 6.
Annual cicadas have undergone some taxonomic tweaking in recent years. They were once placed in the genus, Tibicen. However, that genus now includes only a few European species. Annual cicadas found in the eastern U.S. including Ohio are now placed in the genus, Neotibicen. Those in the western U.S. and Mexico are now grouped in the genus, Hadoa.
Our annual cicadas share several behavioral traits with their periodical cicada cousins. The nymphs of both types of cicadas develop underground sustained by juices sucked from tree roots and it takes multiple years for them to complete their development from eggs to new adults.
However, dog-day cicadas develop more quickly compared to periodical cicadas. It takes 2-3 years for the nymphs to complete their development. Adults emerge every year because of overlapping generations. The adults appear sporadically throughout the “dog days” of summer usually beginning in July. Indeed, the specific epithet, canicularis, is derived from the Latin word, canicula, which references the Dog Star, Sirius.
Dog-day cicada males also "sing" to attract females. However, they do not "chorus" with large numbers synchronizing their song. An occasional dog-day cicada buzzing to entice a female doesn't compare to the cacophony created by a multitude of periodical cicadas. It's like comparing a barbershop quartet to a million-man chorus!
As with periodical cicadas, dog-day cicada females use their long, spade-like ovipositors to insert eggs through the bark of twigs and into the white wood. They can produce twig dieback (“flagging”); however, owing to the smaller numbers, their egg-laying damage usually goes unnoticed.
Dog-Day Cicada Nemesis
The annual arrival of dog-day cicadas also marks the appearance of cicada killer wasps. Cicada killers feed exclusively on annual dog-day cicadas; they do not prey upon periodical cicadas. The synchrony with annual cicadas makes sense if you consider that the wasps would starve to death waiting 13 or 17 years for a periodical cicada meal.
Cicada killers are the largest native wasp found in Ohio measuring 1 1/8 to 1 5/8” in length. As with all Hymenoptera (wasps, bees, etc.), only the females possess stingers (ovipositors); however, they are not aggressive. The males are aggressive, but they lack stingers.
The females spend their time digging and provisioning burrows with paralyzed cicada-prey. They prefer to dig their brood burrows in bare, well-drained soil that is exposed to full sunlight. Although the wasps are considered solitary, all of the females have the same nesting requirements. So it is not unusual for there to be numerous burrows, and wasps, in relatively small areas.
The males spend their time establishing and defending territories that encompass multiple females. They are notoriously defensive and will aggressively buzz any transgressor who dares to enter their territory including other males as well as picnickers, golfers, volleyball enthusiasts, and gardeners. Fortunately, it's all a rouse since they lack the necessary equipment to deliver a sting.
Although the males can't sting, their large size coupled with low-level flights over sand volleyball courts, sparse lawns, and bare areas in landscapes can be disconcerting generating demands for control options. However, insecticide applications to kill the killers are not recommended.
Cicada killers are considered beneficial insects and the females are not aggressive; stinging encounters are extremely rare. If the killers take up residence in a public location, one option is to educate the public. This approach was very successful a few years ago in a park in Hamilton County. Complaints dropped to zero after the sign was posted.
The best way to manage cicada killers if they appear where they're not wanted is to modify their habitat. Renovating lawns late this summer to thicken the turfgrass will keep the killers out of lawns. Applying mulch to cover bare soil or raking mulch to disturb and redistribute possible burrowing sites will convince females to nest elsewhere. The same is true for golf course sand traps and sand volleyball courts. Periodical raking will prevent the wasps from becoming established.